Maximum overload constraint analysis guidance method based on static prediction

Abstract

The invention discloses a maximum overload constraint analysis guidance method based on static prediction, and belongs to the general technical field of guidance control. The implementation method comprises the steps that a sight line coordinate system is defined in a longitudinal plane, an aircraft target relative motion model is established on the basis of the sight line coordinate system, and an overload change prediction result is obtained from aircraft launching, namely starting from a terminal guidance section to hit by taking an initial connecting line as a benchmark and based on an optimal control theory in combination with a multi-constraint optimal terminal guidance expression; based on an overload change prediction result, analyzing a whole-course overload change prediction condition, and judging whether overload exceeds a constraint limit or not; after the overload crosses the boundary, changing the position of the guidance turning point of the aircraft, and judging whether the overload crosses the boundary again until the overload prediction result meets the constraint condition; and a multi-constraint end-section optimal guidance law considering the falling angle constraint is substituted, maximum overload constraint analytical guidance based on static prediction is achieved, the overload of the aircraft in the flight process meets the requirement, and meanwhile the target is hit with the expected falling angle.

Description

Technical Field

[0001] The invention relates to a maximum overload constraint analysis general guidance method based on static prediction, belonging to the general technical field of guidance control. Background Art

[0002] Currently, the use of fixed-wing unmanned aerial vehicles to accurately rendezvous with targets has also become an important requirement for the development of the unmanned aerial vehicle guidance and control field.

[0003] When multi-constraint guidance is required for ground targets, in order to ensure sufficiently high hit accuracy and angle control accuracy, the existing large angle guidance law (shaped guidance law) is used, which places high demands on the maneuverability of the aircraft. Currently, the commonly used fixed-wing unmanned aerial vehicles have limited maneuverability and cannot meet the guidance law requirements, which in turn greatly affects the guidance effect and leads to mission failure. Summary of the invention

[0004] In order to avoid the problem of guidance mission failure caused by overload exceeding the limit during aircraft guidance, the purpose of the present invention is to provide a maximum overload constraint analytical guidance method based on static prediction. Through static dimensionless prediction, the prediction result of the overload of the terminal guidance section is obtained, and then the position of the aircraft guidance turning point is adjusted according to the overload prediction situation, so that the overload of the aircraft meets the requirements during flight and hits the target at the expected landing angle.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] The maximum overload constraint analytical guidance method based on static prediction disclosed by the present invention defines a line of sight coordinate system in a longitudinal plane, and on this basis establishes an aircraft target relative motion model, takes the initial connection line as a reference, based on the optimal control theory, and combines the multi-constraint optimal terminal guidance expression to predict the overload change result from the launch of the aircraft, that is, the beginning of the terminal guidance stage until the moment of impact; based on the overload change prediction result, analyze the overload change prediction situation throughout the process to judge whether the overload exceeds the constraint limit; after the overload exceeds the limit, change the position of the aircraft guidance turning point, and judge whether the overload exceeds the limit again until the overload prediction result meets the constraint condition; substitute the multi-constraint terminal optimal guidance law considering the angle of impact constraint to realize the maximum overload constraint analytical guidance based on static prediction.

[0007] The maximum overload constraint analytical guidance method based on static prediction disclosed in the present invention comprises the following steps:

[0008] Step 1: Establish target relative motion model;

[0009] First, define the line of sight coordinate system Ox q y q z q ; The origin O is located at the center of mass of the aircraft; Oxq The axis points to the direction of the target line; Oy q The axis is located in the vertical plane passing through the origin and is q Axis vertical; Oz q Axis perpendicular to Ox q y q For planes, the positive direction is determined according to the right-hand coordinate system;

[0010] Establish the target relative motion relationship expression in the longitudinal plane, that is, the target relative motion model:

[0011]

[0012] φ=θ-q

[0013] Among them, r is the target connection distance, V T is the target speed, V M is the aircraft speed, q is the angle between the initial target line and the current line, referred to as the sight angle, θ is the velocity inclination, φ is the angle between the aircraft speed direction and the current aircraft target line direction, referred to as the field of view angle, φ T is the angle between the aircraft speed direction and the current aircraft target line direction, a yc Normal overload for the vehicle.

[0014] Step 2: On the coordinate system established in step 1, based on the optimal control theory and combined with the multi-constrained optimal terminal guidance expression, an overload static prediction model is established.

[0015] Predicted overload maximum value It is expressed as the maximum value of the static overload prediction result; the maximum overload constraint a yc-lim It represents the upper limit of the aircraft overload during the entire flight.

[0016] The optimal guidance law expression of the multi-constrained terminal stage considering the angle constraint is as follows:

[0017]

[0018] Among them, V r is the relative speed between the aircraft and the target. For a stationary target, V r =V M , V M is the aircraft speed; is the rate of change of the sight angle, q F is the impact angle in the inertial coordinate system;

[0019] The aircraft flight time t is normalized and dimensionless:

[0020]

[0021] Estimated total flight time

[0022] Combined with the optimal guidance law expression of the multi-constrained terminal stage, the guidance instruction changes over time:

[0023]

[0024] Among them, ε0 is the velocity deviation angle of the aircraft at the initial moment, and the expression is ε0=θ0-q0; θ0 and q0 are the velocity inclination angle and the line of sight angle at the initial moment; q Fc is the impact angle of the aircraft in the line of sight coordinate system defined in step 1, expressed as q Fc =q F -q0.

[0025] According to the relative position relationship between the aircraft and the target, the relationship is as follows:

[0026]

[0027] Among them, the intermediate variable ΔH-H M -H T , H M , H T is the initial height of the aircraft and target; ΔX=X M -X T , X M , X T is the initial horizontal position of the aircraft and the target; Substitute equation (4) into equation (3) to obtain the deformation result of the guidance instruction prediction expression

[0028]

[0029] Based on the relative position relationship between the aircraft and the target, the initial sight angle is expressed as:

[0030]

[0031] Substituting the result of formula (6) into formula (5), the static overload prediction model based on the current relative position relationship between the aircraft and the target and the impact angle can be obtained as follows:

[0032]

[0033] Step 3: Based on the static overload prediction model in step 2 and the initial position of the aircraft at this time, calculate the predicted maximum overload value The absolute value of the predicted maximum overload is compared with the maximum overload constraint a yc-lim Compare and when the judgment result is that the prediction is out of bounds, that is, when the predicted maximum overload value is greater than the overload constraint, execute step 4; otherwise, execute step 5;

[0034] It can be seen from formula (7) that when the position of the aircraft and the target is given, the change of the static overload prediction model is only related to the dimensionless time variable related to is a linear function of the independent variable, so the maximum value appears at the end; therefore,

[0035]

[0036] The maximum overload prediction change obtained by formula (9) The absolute value of the given overload constraint a yc-lim For comparison, The absolute value of is greater than the given overload constraint a yc-lim When the overload exceeds the limit, go to step 4 to adjust the turning point of the aircraft guidance; otherwise, record the initial horizontal position of the aircraft at this time as the feasible horizontal position of the aircraft, go to step 5, calculate the guidance instruction, and then realize the guidance process.

[0037] Step 4: Based on the calculation in step 3 And given the overload constraint a yc-lim Adjust the target position and perform step 3 again.

[0038] When the overload prediction exceeds the limit, that is, When τ, the horizontal position of the guidance turning point is adjusted according to the maximum value of the overload prediction and the overload constraint; the initial horizontal position of the guidance turning point of the aircraft is calculated by X M (τ), τ is an integer and τ ≥ 0; the horizontal distance between the aircraft and the target at the turning point of the guidance step τ is denoted by ΔX(τ); the initial horizontal position of the aircraft at the turning point of the guidance step τ is denoted by X M (τ+1); the next step is to use ΔX(τ+1) to express the horizontal distance of the turning point. Adding an extended term on the basis of ΔX(τ), the expression of ΔX(τ+1) is as follows:

[0039]

[0040] Where η is an additional parameter for controlling the adjustment amplitude; based on the updated result ΔX(τ+1) of the horizontal distance of the guidance turning point obtained by equation (9), the initial horizontal position X of the aircraft in the next step is calculated in reverse M (τ+1); the expression is as follows

[0041]

[0042] Based on formula (10), the initial horizontal position X of the aircraft in the next step is obtained M (τ+1), re-execute step 3 to determine whether an overload or out-of-bounds situation occurs, and make a decision based on the judgment result of step 5.

[0043] Step 5: Substitute the feasible horizontal position of the aircraft obtained in step 3 and the remaining parameters required for the guidance instructions calculated in step 3 into the multi-constrained terminal optimal guidance law expression considering the landing angle constraint in step 2 to obtain the guidance instructions and complete the entire guidance process.

[0044]

[0045] In formula (11), the sight angle q and the sight angle change rate are are obtained through the aircraft's own gyroscope; the relative speed V r , Binding corner q F Substituting into equation (11) we get the guidance command, and according to the guidance command we implement precise guidance based on the static prediction method and considering the maximum overload constraint.

[0046] Beneficial effects:

[0047] 1. The maximum overload constraint analytical guidance method based on static prediction disclosed by the present invention takes the overload static prediction model as the key. On the basis of the pre-given overload constraint, the overload static prediction model is used to judge whether the overload is out of bounds. When the overload is out of bounds, the horizontal position of the aircraft guidance turning point is adjusted based on the predicted maximum value and the overload constraint to finally meet the overload constraint condition.

[0048] 2. The maximum overload constraint analytical guidance method based on static prediction disclosed in the present invention is given a series of initial guidance parameters, and the parameters are processed to obtain the overload static prediction expression. The horizontal position of the aircraft guidance turning point is carefully adjusted according to the proportional relationship between the maximum value of the expression and the overload constraint. After the adjustment, it is judged again until the overload out-of-bounds situation no longer occurs, thereby satisfying the overload constraint in the entire guidance process.

[0049] 3. Based on the optimal control principle, the present invention proposes a general guidance method for maximum overload constraint analysis based on static prediction. First, based on the optimal guidance law expression considering the landing angle constraint, under the condition of a given expected landing angle, a method for real-time prediction of the overload condition of the aircraft throughout the entire process is proposed, which can obtain the estimated value of the change of the aircraft overload throughout the process; then, based on the estimation result, the turning point of the aircraft guidance is adaptively adjusted, thereby significantly reducing the demand for the aircraft maneuvering overload of the guidance mission under the condition of ensuring the accuracy of the hit and landing angle control. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the relative motion model of the aircraft target;

[0051] Figure 2 It is a schematic diagram of the guidance turning point adjustment process;

[0052] Figure 3 It is a schematic diagram of the aircraft overload curve before modifying the guidance turning point;

[0053] Figure 4 It is a schematic diagram of the aircraft overload curve after the guidance turning point is modified;

[0054] Figure 5 It is a schematic diagram of the trajectory curve of the aircraft;

[0055] Figure 6 It is a flow chart of the maximum overload constraint analytical guidance method based on static prediction disclosed by the present invention. DETAILED DESCRIPTION

[0056] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0057] Embodiment 1:

[0058] In this embodiment, the task requirements are: the unmanned aerial vehicle starts at a speed of 100m / s from a height of 1km above the ground, interacts with a ground stationary target 3km away from itself horizontally, performs a guidance task, and the initial speed direction is horizontal. When the task is finally completed, the angle with the horizontal plane is 70°, and the absolute value of the overload throughout the process does not exceed 2g.

[0059] like Figure 6 As shown, the maximum overload constraint analysis and guidance method based on static prediction disclosed in this embodiment has the following specific implementation steps:

[0060] Step 1: Establish target relative motion model;

[0061] First, define the line of sight coordinate system Ox q y q z q ; The origin O is located at the center of mass of the aircraft; Ox q The axis points to the direction of the target line; Oy q The axis is located in the vertical plane passing through the origin and is q Axis vertical; Oz q Axis perpendicular to Ox q y q For planes, the positive direction is determined according to the right-hand coordinate system;

[0062] Establish the target relative motion relationship expression in the longitudinal plane, that is, the target relative motion model:

[0063]

[0064]

[0065] Among them, r is the target connection distance, VT is the target speed, V M is the aircraft speed, q is the angle between the initial target line and the current line, referred to as the sight angle, θ is the velocity inclination, φ is the angle between the aircraft speed direction and the current aircraft target line direction, referred to as the field of view angle, φ T is the angle between the aircraft speed direction and the current aircraft target line direction, a yc Normal overload for the vehicle.

[0066] Step 2: On the coordinate system established in step 1, based on the optimal control theory and combined with the multi-constrained optimal terminal guidance expression, establish an overload static prediction model;

[0067] In this step, the mission requirements are integrated to obtain the following guidance parameters: aircraft speed V M =100m / s, initial height of aircraft H M =1000m, target initial height H T = 0m, the initial horizontal position of the aircraft is X M =0m, target initial horizontal position X T = 3000m, initial trajectory inclination angle θ0 = 0°, binding angle q F =-70°, maximum overload constraint a yc-lim =2g.

[0068] Predicted overload maximum value It is expressed as the maximum value of the static overload prediction result; the maximum overload constraint a yc-lim It is expressed as the upper limit of the aircraft overload during the entire flight;

[0069] The optimal guidance law expression of the multi-constrained terminal stage considering the angle constraint is as follows:

[0070]

[0071] Among them, V r is the relative speed between the aircraft and the target. For a stationary target, V r =V M , V M is the aircraft speed; is the rate of change of the sight angle, q F is the impact angle in the inertial coordinate system;

[0072] The aircraft flight time t is normalized and dimensionless:

[0073]

[0074] Estimated total flight time

[0075] Combined with the optimal guidance law expression of the multi-constrained terminal stage, the guidance instruction changes over time:

[0076]

[0077] Among them, ε0 is the velocity deviation angle of the aircraft at the initial moment, and the expression is ε0=θ0-q0; θ0 and q0 are the velocity inclination angle and the line of sight angle at the initial moment; q Fc is the impact angle of the aircraft in the line of sight coordinate system defined in step 1, expressed as q Fc ≤q F -q0.

[0078] According to the relative position relationship between the aircraft and the target, the relationship is as follows:

[0079]

[0080] Among them, the intermediate variable ΔH=H M -H T , H M , H T is the initial height of the aircraft and target; ΔX=X M -X T , X M , X T is the initial horizontal position of the aircraft and the target; Substitute equation (4) into equation (3) to obtain the deformation result of the guidance instruction prediction expression

[0081]

[0082] Based on the relative position relationship between the aircraft and the target, the initial sight angle is expressed as:

[0083]

[0084] Substituting the result of formula (6) into formula (5), the static overload prediction model based on the current relative position relationship between the aircraft and the target and the impact angle can be obtained as follows:

[0085]

[0086] Step 3: Based on the static overload prediction model in step 2 and the initial position of the aircraft at this time, calculate the predicted maximum overload value The absolute value of the predicted maximum overload is compared with the maximum overload constraint a yc-lim Compare and when the judgment result is that the prediction is out of bounds, that is, when the predicted maximum overload value is greater than the overload constraint, execute step 4; otherwise, execute step 5;

[0087] It can be seen from formula (7) that when the position of the aircraft and the target is given, the change of the static overload prediction model is only related to the dimensionless time variable related to is a linear function of the independent variable, so the maximum value appears at the end; therefore,

[0088]

[0089] The maximum overload prediction change obtained by formula (9) The absolute value of the given overload constraint a yc-lim For comparison, The absolute value of is greater than the given overload constraint a yc-lim When the overload exceeds the limit, the process goes to step 4 to adjust the turning point of the aircraft guidance; otherwise, the initial horizontal position of the aircraft is recorded as the feasible horizontal position of the aircraft, and the process goes to step 5 to calculate the guidance instruction, thereby realizing the guidance process;

[0090] Step 4: Based on the calculation in step 3 And given the overload constraint a yc-lim Adjust the target position and then perform step 3 again;

[0091] When the overload prediction exceeds the limit, that is, When τ, the horizontal position of the guidance turning point is adjusted according to the maximum value of the overload prediction and the overload constraint; the initial horizontal position of the guidance turning point of the aircraft is calculated by X M (τ), τ is an integer and τ ≥ 0; the horizontal distance between the aircraft and the target at the turning point of the guidance step τ is denoted by ΔX(τ); the initial horizontal position of the aircraft at the turning point of the guidance step τ is denoted by X M (τ+1); the next step of the horizontal distance of the turning point is expressed by ΔX(τ+1). In this embodiment, the additional parameter for controlling the adjustment range is η=0.1. Adding an extended term on the basis of ΔX(τ), the expression of ΔX(τ+1) is as follows:

[0092]

[0093] Where η is an additional parameter for controlling the adjustment amplitude; based on the updated result ΔX(τ+1) of the horizontal distance of the guidance turning point obtained by equation (9), the initial horizontal position X of the aircraft in the next step is calculated in reverse M (τ+1); the expression is as follows

[0094]

[0095] Based on formula (10), the initial horizontal position X of the aircraft in the next step is obtained M (τ+1), re-execute step 3 to determine whether an overload or out-of-bounds situation occurs, and make a decision based on the judgment result of step 5;

[0096] Step 5: Substitute the feasible horizontal position of the aircraft obtained in step 3 and the remaining parameters required for the guidance command calculated in step 3 into equation (1) in step 2 to obtain the guidance command and complete the entire guidance process;

[0097]

[0098] In formula (11), the sight angle q and the sight angle change rate are can be obtained by the aircraft's own gyroscope; therefore, the relative speed V r , Binding corner q F Substituting into equation (11) we can get the guidance command, and finally realize the precise guidance considering the maximum overload constraint based on the static prediction method.

[0099] In formula (11), the sight angle q and the sight angle change rate are All of them can be obtained by the aircraft's own gyroscope and do not need to be given; therefore, the relative speed V r , Binding corner q F Substituting into equation (11) we can get the guidance command, and finally realize the precise guidance considering the maximum overload constraint based on the static prediction method. Figure 3 The overload schematic curve before the guidance turning point is modified is given, and the overload exceeds the limit. Figure 4 The schematic curve of overload after the guidance turning point is modified is given, and the overload satisfies the maximum constraint condition at this time; Figure 5 The flight trajectory of the aircraft after the guidance turning point is modified is given.

[0100] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A maximum overload constraint analytical guidance method based on static prediction, characterized in that: The following steps are included: Step 1: Establish target relative motion model; First, define the line of sight coordinate system Ox q y q z q ; The origin O is located at the center of mass of the aircraft; Ox q The axis points to the direction of the target line; Oy q The axis is located in the vertical plane passing through the origin and is q Axis vertical; Oz q Axis perpendicular to Ox q y q For planes, the positive direction is determined according to the right-hand coordinate system; Establish the target relative motion relationship expression in the longitudinal plane, that is, the target relative motion model: φ=θ-q Among them, r is the target connection distance, V T is the target speed, V M is the aircraft speed, q is the angle between the initial target line and the current line, referred to as the sight angle, θ is the velocity inclination, φ is the angle between the aircraft speed direction and the current aircraft target line direction, referred to as the field of view angle, φ T is the angle between the aircraft speed direction and the current aircraft target line direction, a yc Normal overload for the aircraft; Step 2: On the coordinate system established in step 1, based on the optimal control theory and combined with the multi-constrained optimal terminal guidance expression, establish an overload static prediction model; Step 3: Based on the static overload prediction model in step 2 and the initial position of the aircraft at this time, calculate the predicted maximum overload value The absolute value of the predicted maximum overload is compared with the maximum overload constraint a yc-lim Compare and when the judgment result is that the prediction is out of bounds, that is, when the predicted maximum overload value is greater than the overload constraint, execute step 4; otherwise, execute step 5; Step 4: Based on the calculation in step 3 And given the overload constraint a yc-lim Adjust the target position and then perform step 3 again; Step 5: Substitute the feasible horizontal position of the aircraft obtained in step 3 and the remaining parameters required for the guidance instructions calculated in step 3 into the multi-constrained terminal optimal guidance law expression considering the landing angle constraint in step 2 to obtain the guidance instructions and complete the entire guidance process.

2. The maximum overload constraint analytical guidance method based on static prediction according to claim 1, characterized in that: Step 2 is implemented as follows: Predicted overload maximum value It is expressed as the maximum value of the static overload prediction result; the maximum overload constraint a yc-lim It is expressed as the upper limit of the aircraft overload during the entire flight; The optimal guidance law expression of the multi-constrained terminal stage considering the angle constraint is as follows: Among them, V r is the relative speed between the aircraft and the target. For a stationary target, V r =V M , V M is the aircraft speed; is the rate of change of the sight angle, q F is the impact angle in the inertial coordinate system; The aircraft flight time t is normalized and dimensionless: Estimated total flight time Combined with the optimal guidance law expression of the multi-constrained terminal stage, the guidance instruction changes over time: Among them, ε0 is the velocity deviation angle of the aircraft at the initial moment, and the expression is ε0=θ0-q0; θ0 and q0 are the velocity inclination angle and the line of sight angle at the initial moment; q Fc is the impact angle of the aircraft in the line of sight coordinate system defined in step 1, expressed as q Fc =q F -q0; According to the relative position relationship between the aircraft and the target, the relationship is as follows: Among them, the intermediate variable ΔH=H M -H T , H M , H T is the initial height of the aircraft and target; ΔX=X M -X T , X M , X T is the initial horizontal position of the aircraft and the target; Substitute equation (4) into equation (3) to obtain the deformation result of the guidance instruction prediction expression Based on the relative position relationship between the aircraft and the target, the initial sight angle is expressed as: Substituting the result of formula (6) into formula (5), the static overload prediction model based on the current relative position relationship between the aircraft and the target and the impact angle is obtained as follows:

3. The maximum overload constraint analytical guidance method based on static prediction according to claim 2, characterized in that: Step 3 is implemented as follows: According to formula (7), when the positions of the aircraft and the target are given, the change of the static overload prediction model is only related to the dimensionless time variable related to is a linear function of the independent variable, so the maximum value appears at the end; therefore, The maximum overload prediction change obtained by formula (9) The absolute value of the given overload constraint a yc-lim For comparison, The absolute value of is greater than the given overload constraint a yc-lim When the overload exceeds the limit, go to step 4 to adjust the turning point of the aircraft guidance; otherwise, record the initial horizontal position of the aircraft at this time as the feasible horizontal position of the aircraft, go to step 5, calculate the guidance instruction, and then realize the guidance process.

4. The maximum overload constraint analytical guidance method based on static prediction as claimed in claim 3, characterized in that: Step 4 is implemented as follows: When the overload prediction exceeds the limit, that is, When τ, the horizontal position of the guidance turning point is adjusted according to the maximum value of the overload prediction and the overload constraint; the initial horizontal position of the guidance turning point of the aircraft is calculated by X M (τ), τ is an integer and τ ≥ 0; the horizontal distance between the aircraft and the target at the turning point of the guidance step τ is denoted by ΔX(τ); the initial horizontal position of the aircraft at the turning point of the guidance step τ is denoted by X M (τ+1); the next step is to express the horizontal distance of the turning point of the guidance by ΔX(τ+1); adding an extended term on the basis of ΔX(τ), the expression of ΔX(τ+1) is as follows Where η is an additional parameter for controlling the adjustment amplitude; based on the updated result ΔX(τ+1) of the horizontal distance of the guidance turning point obtained by equation (9), the initial horizontal position X of the aircraft in the next step is calculated in reverse M (τ+1); the expression is as follows Based on formula (10), the initial horizontal position X of the aircraft in the next step is obtained M (τ+1), re-execute step 3 to determine whether an overload or out-of-bounds situation occurs, and make a decision based on the judgment result of step 5.

5. The maximum overload constraint analytical guidance method based on static prediction according to claim 4, characterized in that: In step 5, The guidance instruction is shown in formula (11): In formula (11), the sight angle q and the sight angle change rate are are obtained through the aircraft's own gyroscope; the relative speed V r , Binding corner q F Substituting into equation (11) we get the guidance command, and according to the guidance command we implement precise guidance based on the static prediction method and considering the maximum overload constraint.

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